Temperature control device



w.'J. ETTINGER ET Al. 2,061,419

TEMPERATURE CONTROL DEVICE Nov'. 17, 1936.

Filed Dec. 3l, 1954 2 Sheets-Sheet 1 llll lnventors:

Wallace J. EttnQer;

Nicholas Miller,

Their` AttOFneg.

NOV. 17, 1936. W, 1 ETT|NGER ET'AL 2,061,419

TEMPERATURE CONTROL DEVICE Filed Deo. 3l, 1954 2 Sheets-Sheet 2lrwencos: l Wallace J. Etimger Nicholas Miller;

bg fr( The AttOr-rweg.

Patented Nov. 17, 1936 TEMPERATURE CONTROL DEVICE Wallace J. Ettinger,Chicago,

and Nicholas Miller, La. Grange, Ill., assignors to Edison GeneralElectric Appliance Company, Chicago, Ill., a corporation of New YorkApplication December 31, 1934, Serial No. 759,932

8 Claims. (Cl. 20G-138) This invention relates to temperature controldevices, more particularly to devices for controlling an electriccircuit in accordance with temperature changes, and it has for itsobject the provision of an improved device of this character.

In general, this invention relates to temperature responsive devices,such as described and claimed in United States reissue patent to A.Lewerenz, No. 16,654, dated June 14, 1927. More specifically, thisinvention relates to improvements in the temperature control devicedescribed and claimed in United States patent to Francis H. McCormickNo. 1,977,394, dated October 16, 1934. The temperature control devicesdisclosed in these patents comprise a bimetallic thermostat bar fixed atone end and having its other end free to move in response to changes intemperature. The movement of the bimetallic bar in response totemperature changes is used to control a suitable switch or othercontrol member. Bearing on the movable end of the bimetallic bar is anelastic member arranged to cause the bar to move quickly from oneposition to another and thereby give the switch a snap action in openingand closing the circuit which it controls.

In the above-mentioned McCormick patent, means are provided foradjusting the temperature setting of the device by adjusting therelative position of the thermostat bar and the elastic member whichbears on the movable end of the bar.

This invention contemplates the provision of a thermostat provided withimproved temperature adjusting means of this character.

Another aspect of this invention is the provision of a new organizationin a temperature control device of this type including the provision ofimproved means for adjusting the relative position of the thermostat barand the spring i which bears upon it.

Still another aspect of this invention is the provision of improvedmeans providing an oi position of the thermostat, that is, a position ofthe thermostat wherein the switch associated with it is held in its openposition.

In accordance with this invention, the bimetallic bar in one form issecured to a heat conducting supporting member which is adapted to beclamped or secured directly in thermal relation with the heated body ordevice whose temperature is to be controlled. In another form, thebimetallic bar is secured to a member which has a low heat condiltivityand arranged S9 that the bar can be clamped directly to the heated bodywhose temperature is to be controlled. Mounted upon the supportingmember is a suitable support for the spring which bears on the movableend of the thermostat bar to cause it to move quickly from one positionto another. This support for the spring is pivotally mounted to thesupporting member whereby it can be adjusted on the supporting member toadjust the position of the spring relative to the thermostatic bar. Thesupport for the spring in one form of this invention is in the form of ayoke embracing the thermostat bar. This yoke is provided with a bearingfor the spring positioned on the yoke opposite the free end of thebimetallic bar. An adjusting screw is threaded into the supportingmember and is connected with the yoke so that the position of the yokeis determined by the adjustment of the screw.

In one form of this invention, the yoke carries a suitable switchcontact with which a contact carried by the bimetallic bar cooperates. Asuitable spring is interposed between the adjusting screw and the yokeproviding for movement of the yoke relative to the adjusting screw, whenthe switch contacts are closed and when the birnetallic thermostat barhas a predetermined temperature condition so as to obviate the settingup of excessive stresses in the bar.

An on position of the temperature control device is effected by means ofa stop arranged to engage the thermostatic bar when the adjusting screwhas been operated to effect a predetermined low temperature setting ofthe control device.

For a more complete understanding of this invention, reference should behad to the accompanying drawings, in which Fig. 1 is a verticalelevation mainly in section of a temperature control device embodyingthis invention; Fig. 2 is a plan View of the temperature control deviceshown in Fig. 1, portions being broken away and parts shown in sectionso as to illustrate certain details of construction; Fig. 3 is avertical sectional view taken through the line 3--3 of Fig. 2; Fig. 4 isa vertical elevation mainly in section illustrating a modied form ofthis invention; Fig. 5 is a plan view of the temperature control deviceshown in Fig. 4; Fig. 6 is a plan view of a portion of the temperaturecontrol device of Figs. 4 and 5; and Fig. 7 is a sectional view takenthrough the portion of the control device shown in Fig. 6.

Referring more particularly to Figs. 1, 2 and 3 of the drawings, thisinvention has been shown in one form as applied to a. temperatureresponsive device intended to be used to control the energizing circuitoi' an electrically heated device, such as a tlatiron. It is to beunderstood, however, that this invention is not limited to thisapplication, but has general application. In Figs. l, 2 and 3, the bodymember I8 is part oi the sole plate oi an electrically heated i'latiron,the details of which have not been illustrated, since they form no partof this invention. In the upper portion of the body member I8 is arecess I I in which is secured a temperature responsive control devicearranged in acoordancc with this invention to control the heatingcircuit of the iron with which the control device is associated. Asshown. the temperature control device comprises a suitable thermostat,shown as a bimetaliic bar I2 made oi two strips o! metal havingdissimilar temperature coefiicients o! expansion, such as invar andsteel, the strips being securely bramed or welded together lengthwise.

The thermostatic bar I2 is rigidly secured at one end to a supportingbase or trame I8. The base or trame I8 is provided with a recess I8which reeeives the thermostatic bar, and the bar is clamped between thebase I8 and a plate Il by means oi' a pair of rivets I8, which, as shownmore clearly in Pig. 1, are passed through apertures provided for themin the bimetallic bar I2. the support I8, and the clamping plate I8.'I'he supporting plate I8 with the thermostatic bar I2 rigidly securedthereto is adapted to be clamped in direct thermal relation with theheated body I8. For this purpose, the supporting plate I8 and theclamping plate Il are provided with a pair of apertures on oppositesides of the channel I8 receiving the thermostat, and through theseapertures are directed a pair oi' clamping studs I1, which are arrangedto be received in threaded relation with the body I8. It will beobserved in view of this arrangement that the thermostatic bar I2 isclamped in direct thermal relation with the body I8 so that heat isconducted to it directly from the body. It will also be observed thatthe thermostatic bar -is supported in the recess II in close thermalrelation with the working body of the iron.

I'he end o! the thermostat opposite to that secured to the plate I8 isfree to move laterally in response to changes in temperature. This freeor movable end of the thermostatic bar is provided with a knife-edgebearing I8 on which a suitable compression spring I8 is arranged tobear. As shown, the spring i8 bears directly on a collar 2li which isprovided with a seat 2i to receive the knife-edge bearing I8 on thethermostat bar. The opposite end of the spring I8 rests upon a similarcollar 22 which is provided with a bearing seat 28 that receives aknife-edge bearing 28. The bearing 28 is provided with a shank 25 whichis circular in cross-section, and which is received in a similarlyshaped bore provided for it in an adjusting stud 28. The adjusting stud28 is secured directly to the yoke 21. It will be observed that thetension in the compression spring I9 can be varied by varying theposition of the stud 26 in the yoke 21. The stud 28 is secured in itsadjusted position in the yoke by means of the nut 26a.

As shown clearly in Fig. 2, the yoke 21 in plan has a substantiallyU-shape, the yoke being provided with a pair of arms 28 arranged onopposite sides of the thermostatic bar I2 and an arm 28 connecting theside arms 28, and being arranged to directly support the bearing 28 forthe spring I8. The ends oi the side arms 28 opposite the arm 28 areplvotally mounted on a pin 80 which in turn is supported in up-rightIlanges 8| provided on the supporting member I8. I'he side arms 28 arejoined intermediate their ends by means of a top or cover plate 82.Preferably, the side arms 28, the end arm 28, and the top plate 82 willbe formed of a single piece of metal.

In view o! the foregoing construction, it will be observed that the yoke21 is pivoted to the supporting plate I8 adjacent the rigid or securedend of the blmetallic bar I2 and that it embraces the bar between itsside arms 28 and the end arm 28 connecting the side arms. It will alsobe noted that the yoke has such a length that a space is providedbetween the bearing I8 on the bimetallic bar I2 and the bearing 28carried by the yoke suiiiciently great to receive the compression springI8.

I'he position of the yoke 21 is adjusted by means of an adjusting screw88 which is received in threaded engagement by the supporting member I8.This member i8, as shown in the drawings. is provided with a portion 88extending laterally over the thermostatic bar I2 towards its movableend. 'Ihe adjusting screw 88, as shown, is provided with a threadedportion 88a at its lower end which is received in this portion o! thesupporting member. Above the threaded portion 88a. there is provided arecess 8l which defines an abutment 88 positioned directly above thethreaded portion 88a. 'Ihe reduced portion 88 of the screw is receivedin a slot 81 provided for it in the top plate 82 of the yoke, the widthot the slot being slightly greater than the diameter of the reducedsection 88. 'I'he top plate 82 is biased into engagement with theabutment 88 by means oi a compression spring which has its l' lower endbearing on the top plate 82 and its upper end on a suitable stop orabutment 8l mounted on the adjusting screw. As shown. the abutment 88 isformed as a collar surrounding the adjusting screw, and is securedagainst vertical movement by means of a suitable stop 8II mounted on thescrew. The screw 88 is free to turn relative to the collar 88, which isheld against rotation with the screw by means oi a pin 8l which isrigidly secured in a substantially upright position to the supportingmember I8. The collar is provided with an extension 82 in which there isprovided an aperture 88 for receiving the pin 8|. The upper end of theadjusting screw 88 is provided with a knurled portion 88 which isarranged to receive a suitable knob or adjusting handle (not shown) andwhich is provided with a knurled aperture to iit the knurled portion 88.

It will be observed that the position oi' the yoke 21 will be determinedby adjusting the position of the screw 88. If it be desired to move theyoke 21 in a clockwise direction, as viewed in Figs. 1 and 3. it ismerely necessary to turn the screw 88 inwardly on the supporting memberI8. This operation, of course, will lower the abutment 88 so as to allowthe top plate 82 to be moved in a clockwise direction by means of thecompression spring 88. Adjustment of the screw 88 in the oppositedirection, that is away from the supporting plate I8, will move the yokein a counter-clockwise direction. Suitable stops 88 and 86 are securedto the upper end portion oi' the adjusting screw and are arranged toengage the pin 8| so as to limit the range of movement of the adjustingscrew.

The provision of the abutment 89 movable up and down with the screw asit is adjusted to move the yoke 21 up and down is an important featurein that the spring 88 is compressed to the same degree irrespective ofthe adjustment of the yoke. Further functions of the spring 38 will bepointed out in greater detail hereinafter.

The yoke 21 carries a `pair of spaced contacts 41 which are secureddirectly to a plate 48 formed of any suitable electrically insulatingmaterial, such as mica. The contacts 41 may be in the form of rivetssecured to the insulating plate 48, as shown more clearly in Figs. 1 and2, and their upper ends pass through a suitable aperture 49 provided forthem in the top plate 32. The insulating plate 48 is rigidly secured tothe top plate by means of rivets 58. A pair of suitable supply terminalsor leads 5I are secured to the contacts 41. Preferably, these memberswill be formed of relatively thin metallic strips, as shown, andpreferably they will be directed to the under side of the insulatingplate 48 through suitable apertures or slits 52 provided for them in theplate. The portions of the leads 5I beneath the plate 49 are rigidlysecured to the contacts 41, as clearly shown in Figs. l and 2.

It will be understood that the leads 5I will be connected in the heatingcircuit of the fiatiron in this case. However, it is to be understoodthat they may be connected in any circuit to be controlled or in acontrolling circuit for the circuit to be controlled.

A suitable bridging contact 53 for the contacts 41 is carried by thefree end of the bimetallic bar I2. The bridging contact 53 is supportedby bracket 54 which in turn is rigidly secured to the bimetallic bar I2by means of rivets 55. The bracket 54 is electrically insulated from thebar I2 by means of sheets of insulating material 55 formed of anysuitable insulating substance, such as mica. The contact 53 is mountedin the bracket 54 for pivotal movement on an axis parallel with thethermostat bar I2. The contact 53, as shown, is provided with acontacting surface 53a formed of a precious metal, such as ne silver,which is secured in any suitable manner to a backing 53b formed of anysuitable common metal, such as bronze.

It will be observed that when the bimetallic bar I2 is in its positionshown in Figs. l and 3, the contact 53 will bridge the xed contacts 41so as to complete an electric circuit through the temperature controldevice. And that when the bimetallic bar I2 is operated to move thebridging Contact 53 away from the contacts 41, the electrical circuitthrough the temperature control device will b e interrupted. Thebimetallic bar I2 in the specific form of the invention illustrated isso arranged that when the temperature is below a predetermined maximumit will hold the contact 53 in engagement with the contacts 41, whereaswhen its temperature has been increased to a predetermined maximum, itwill operate to move the bridging contact 53 away from fixed contacts41. A suitable stop member 51 is provided for limiting the movement ofthe bimetallic bar I2 away from the contacts 41. This stop member, asshown, comprises a stud which is threaded in a suitable supportingbracket 58 which in turn is rigidly secured to one arm 28 of the yoke21.

It will be understood that the compression spring I9 functions to movethe bimetallic bar I2 quickly with a snap action between its switchopening and closing positions. 'I'he bearing 24 carried by the yoke 21lies in the plane of movement of the bimetallic bar I2 in such'aposition that at a predetermined temperature the knifeedge bearing I8 onthe bar I2 will lie in a line passing through the bearing 24 to thepoint of support of the bar I2. This position is known as the neutralposition of the thermostatic bar. The compression spring I9 exerts aforce on the movable end of the thermostatic bar I2 which tends to holdthe movable end of the bar on one side or the other of this neutralposition. When the bar is substantially in the neutral position, theentire force exerted by the spring member is in the direction of thepoint of support of the thermostat, and consequently, in this positionthe spring exerts substantially no force on the bar tending to move itto one or the other of its controlling positions. However, when thethermostat moves from the neutral position in either direction, alateral component of the spring pressure is produced tending to forcethe thermostat away from the neutral position. It is this action of thespring member I9 that causes the thermostat bar to move quickly with asnap action between its controlling positions.

In the operation of the control device, as shown in Figs. 1, 2 and 3, itwill be understood that the movable contact 53 will be held upwardagainst the contact 41 to maintain the heating circuit of the heatingdevice closed as long as the temperature is below a predeterminedmaximum. Under these conditions, the movable end of the thermostat baris situated above the neutral position. As the temperature increases thedistortion of the thermostat bar tends to move its free end downward,but this movement is resisted by the resilient member I9. Upon theoccurrence of a predetermined maximum temperature, however, thethermostat has suilicient force to overcome the spring I9 when it startsto move downward. As the thermostat moves downward. the opposing forceexerted by the spring I9 decreases whereby the thermostat rapidlyaccelerates and moves at a high speed through the neutral position tothe opposite side thereof where it is urged rapidly downwardly by theincreasing lateral component of the force applied by the spring I9. Theheating circuit is thus quickly opened, the movable contact 53 beingthrown downward to its open circuit position. After the heating circuithas been opened and the temperature of the heating device andconsequently that of the thermostat decreases, the distortion of thethermostat tends to move it back to its closed circuit position. Uponthe occurrence of a predetermined minimum temperature, the thermostatwill snap to its closed circuit position. In this manner the heatingcircuit is controlled to maintain a predetermined temperature which is amean between the maximum and minimum temperatures for which the deviceis set to operate. The range between the maximum and minimumtemperatures is adjusted by adjusting the position of the screw 26, aspointed out in greater detail in the above Lewerenz patent.

The control device can be set to maintain a desired predeterminedtemperature by means of the adjusting screw 33. It will be observed thatwhen the rod 33 is rotated, the position of the yoke 21 and hence theposition of the knife-edge bearing 24 is changed. This operation changesthe position of the neutral line between the knifeedge bearing 24 andthe point of support of the thermostatic bar I2. Thus, the temperatureat which the thermostat bar I2 will snap from one position to the otherthrough the neutral line is changed. Consequently, the temperaturemaintained in the heated body I0 will be changed. To

set the device to maintain a higher temperature, the adjusting screw 33is turned downwardly so as to move the knife-edge support 24 downwardly.Adjustment of the screw 33 in the opposite direction will decrease thetemperature setting of the temperature control device.

In order to provide an open position of the switch that is, an olfposition for the control device, a suitable stop 59 is provided. Thestop 55, as shown, is in the form of an arm or bar, one end, theleft-hand end, as viewed in the figures, of which is rigidly secured tothe supporting member Il. The arm is arranged on one side of thethermostat bar, as shown in Fig. 2, and is arranged substantially inparallel relation with the bar. The thermostat bar carries a member 5lwhich under certain conditions of operation is arranged to engage thestop 59. The member Il, as shown, is mounted in a supporting bracket 5Iwhich in turn is rigidly secured to the end of the thermostat bar I2 bymeans of the rivet 55. When the adjusting rod I3 is operated to moveaway from the plate I3 and thereby elevate the yoke 21 to etfect lowertemperature settings, the thermostat bar I2 of course will be forced tofollow the yoke upwardly by the action of the spring Il. When the screw33 has been moved a predetermined distance from the plate I3, the member60 carried by the bar I2 will engage the stop 59 carried by the supportI5, whereupon if the screw 3l be further adjusted into its lowtemperature range, the yoke 21 will continue to move upwardly while thethermostat bar I2 will be held stationary by the stop. As a result ofthis the contacts l will be carried away from the bridging contact 5I.This constitutes the "oil" or open condition of the control device. Inorder to reclose the switch it is merely necessary to turn the adjustingscrew 33 in a direction to increase the temperature setting until theclearance between the contacts 41 and 53 is absorbed. whereupon theswitch will be closed.

It will be observed that during the normal operation of the controldevice, the compression spring I8 holds the yoke 21 against the abutmentl5. The spring, however, permits the yoke to move relatively to theadjusting screw under certain conditions of operation. This occurs whenthe thermostat has been set for a high temperature and is then allowedto cool to room temperature, as, for example, when the iron is detachedfrom its supply source. Under these conditions, when the bar I2 cools,it, of course, causes the bridging contact 53 to bear againstthecontacts 41 with an increasing force. The stress ln the bar, due tothis action increases and unless relieved would unduly stress the barand in certain cases might even produce a permanent set. 'I'he spring 38relieves this excessive stress in the bar by permitting the yoke to moveupwardly when the stress in the bar attains a predetermined maximum. Thereduced portion 25 provides for movement of the yoke relative to thescrew 33.

In the form of this invention shown in Figs. 4 to 7, inclusive, thebimetallic bar 62 has one end rigidly secured, as by welding, to asupport il and the support and bar are rigidly secured to the body 60whose temperature is to be controlled by means of a clamping screw 55.In this case, the support 63 is positioned directly above the bimetallicbar 62, which, as shown, bears directly on the heated body 64. Thebimetallic bar 62 carries on its free or movable end a knife-edgebearing 55. Bearing on this movable end of the bar is a U-shapedcompression spring 81, one arm of which, as shown, rests upon theknife-edge bearing 5l and its other arm upon a bearing 68 carried by ayoke 55. 'Ihe leg of the U-shaped spring 61 bearing upon the bimetallicbar 62 at its lower end is provided with two spaced feet 10 (Fig. 5) ineach of which is provided a bearing seat 1I. The other leg of the spring61 is provided with a seat I2 in which is received a ball bearing I3that is carried by a stud 14. This stud Il is rigidly supported by theyoke 88. Preferably, the stud will be provided with a bore 14a forreceiving the ball, and preferably and as shown. two balls 1I will bepositioned in the bore and arranged so that the outer ball supports thespring l'l clear of the stud. 'Ihe ball bearing decreases frictionbetween the spring 51 and the supporting stud 14.

The yoke 59 has in general the same shape as has the yoke 2I of the rstform described. and is pivotally mounted to the supporting bracket 6I bymeans of a pin 15. The upper plate 16 of the yokeis secured to anadjusting screw 'l1 which has threaded engagement with the support I3,as shown in Fig. 4. The adjustlng screw at its lower end is providedwith an abutment 'I8 above which is provided a reduced portion Il thatreceives the top plate 1l. 'nie top plate 'I6 is biased into engagementwith the abutment 18 by means of a compression spring that has its lowerend bearing on the top and its other end bearing against the supportingbracket 5l.

The top plate 'I0 carries a pair of spaced contacts 8| which aresupported directly by means of an insulating member B2. formed of anysuitable electrically insulating material. This member in turn isrigidly secured to the top plate II by means of.screws 8l. Cooperatingwith the spaced contacts 8l is a bridging contact Il carried by themovable end of the bimetallic bar 52. 'I'he bridging contact 8l issimilar in construction to the bridging contact 5I of the first form.The contact Il is carried by a U-shaped bracket which is secured to theend of the bimetallic bar by means of a rivet 56. This bracket isinsulated from thebimetallic bar by insulating sheets l1. The contact 8lcan rotate in the bracket l5 to alimited extent on an axis parallel withthe bar 82.

On the upper end of the adjusting screw 'I1 is provided an indicatingdial 8l which cooperates with a fixed index 89 carried by the support Ilto assist in adjusting the temperature of the control device. A suitablestop 5l provided on this dial is arranged to engage the indicator orfixed index 89 so as to limit the range of movement of the adjustingscrew.

This device operates in the same fashion as the control device shown inFigs. l. 2 and 3. It is believed to be unnecessary to describe in detailthe operation of the second form. Briefly, the bimetallic bar 62 lsmoved between its controlling positions with a snap action by theoperation of the spring 61. The temperature setting of the device iseffected by adjusting the position of the yoke i5, which as previouslydescribed, changes the neutral position of the thermostat. The spring 80functions to prevent undue stress in the bimetallic bar in substantiallythe same manner as does the spring 2l of the first form.

An important feature of this invention is the organization wherein allthe elements of the control device are supported on a single supportingmember I3 (Figs. 1-3), 63 (Figs. 4 and 5), and the whole being arrangedto be applied to an appliance by simple clamping screws. In each form,the bimetallic bar is supported in intimate thermal relation with theheated body Whose temperature is to be controlled. In the second formwhere the support 63 is above the thermostat it is preferable to formthe support of a metal having a relatively low heat conductivity.

While We have shown particular embodiments of our invention, it will beunderstood, of course, that we do not Wish to be limited thereto sincemany modifications may be made, and we, therefore, contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States, isz- 1. A temperature control device comprising athermostat, an elastic member arranged to cause said thermostat to movequickly from one position to another, a support for said elastic member,means for varying the position of said support so as to adjust thetemperature setting of said device, a stop carried by said supportagainst which said thermostat bears when it has a predeterminedtemperature condition and means yieldingly holding said support againstthe force of said thermostat arranged to permit movement of said supportby said thermostat when the force exerted by said thermostat on saidstop attains a predetermined maximum.

2. A temperature control device comprising a thermostat bar having oneend fixed and its other end free to move in response to changes intemperature, a spring having one end bearing on said bar and movablewith said bar in its plane of movement so as to cause said bar to movequickly from one position to another, a support for the other end ofsaid spring, a substanstantially rigid pivoted lever carrying saidsupport for movement in said plane of movement of said thermostatic bar,an adjusting screw connected with said lever for shifting its positionin said plane of movement, a stop carried by said lever against whichsaid thermostat bar rests when it has a predetermined temperaturecondition and a spring between said adjusting screw and said leverproviding for movement of said lever relative to said screw by saidthermostat bar under predetermined temperature conditions of said bar.

3. A temperature control device comprising a thermostat bar having oneend fixed and its other end free to move in response to changes intemperature, a spring having one end bearing on said bar and movablewith said bar in its plane of movementso as to cause said bar to movequickly from one position to another, a support for the other end ofsaid spring, a substantially rigid pivoted member carrying said supportfor movement in said plane of movement of said thermostat bar, anadjusting screw having an abutment thereon arranged to engage saidpivoted member to shift its position in one direction in said plane ofmovement, a spring carried by said adjusting screw bearing on said leverto hold it against said abutment so as to move said lever in theopposite direction when said abutment is moved in said oppositedirection by said adjusting screw, a switch contact carried by saidlever, a switch contact carried by said thermostat bar engaging saidcontact on said lever when said thermostat bar has a temperature below apredetermined maximum so as to tend to move said lever in said onedirection, said spring carried by said screw permitting said lever to bemoved by said thermostat bar in said one direction when the forces setup in said bar urging said switch contacts together exceed apredetermined maximum, and a stop carried by said lever arranged toengage said thermostat bar to limit its movenient away from said contacton said lever.

4. A temperature control device comprising a heat conducting supportingmember adapted to be clamped in direct thermal relation with a body tobe heated, a bimetallic thermostat bar having one end rigidly secured tosaid supporting member and its other end extending laterally therefromand free to move in response to changes in temperature, a rigid yokepivotally secured to said supporting member adjacent the fixed end ofsaid thermostat bar for movement in the plane of movement of said barand having a pair of arms extending laterally from said member onopposite sides of said bar with their ends extending beyond the end ofsaid bar and a third arm connecting the extending ends of said pair ofarms beyond the end of said bar, a compression spring interposed betweenthe end of said bar and said third arm, a top plate overlying said barconnecting said pair of arms at the sides, an adjusting screw passedthrough an aperture provided for it in said top plate and received inthreaded engagement in said supporting member, an abutment on said screwbearing on the underside of said top plate, a second abutment on saidscrew spaced from the upper surface of said top plate and a compressionspring interposed between said second abutment and said top plate.

5. A temperature control device comprising a thermostat bar having oneend xed and its other end free to move in response to changes intemperature, a spring having one end bearing on said bar and movablewith said bar in its plane of movement so as to cause said bar to movequickly from one position to another, a support for the other end ofsaid spring, a substantially rigid pivoted member carrying said supportfor movement in said plane of movement of said thermostat bar, anadjusting screw having an abutment thereon arranged to engage saidpivoted member to shiftits position in one direction in said plane ofmovement when said screw is turned in one direction, a second abutmentxed on said screw so as to move with it when said screw is adjusted, anda spring between said second abutment and said member biasing saidmember into engagement with said first abutment, the tension in saidspring remaining unchanged when said screw is turned to adjust theposition of said member.

6. A temperature control device comprising a thermostat bar, a switchoperated by said thermostat bar related to said bar so that when saidbar is cooled to a temperature below a predetermined value said baroperates to close said switch, a spring acting on said thermostat ba rso as to move said switch quickly from its closed to its open positionand from its open to its closed position depending upon the relativeposition of said thermostat bar and said spring, adjusting means foradjusting the relative position of said thermostat bar and spring in onedirection so as to increase the temperature setting of said device andin the opposite direction to decrease the temperature setting of saiddevice and a stop for engaging said thermostat bar when said relativeposition has been adjusted in said opposite direction a predeterminedamount to prevent further movement of said bar so that said switch isopened by further adjustment in the relative position of said bar andspring in said opposite direction.

7. A temperature control device comprising a thermostat. a U-shapedspring having a pair of spaced apart feet on one leg bearing on saidthermostat, and a bearing for the other leg of said spring comprising asupport, a ball bearing carried by said support and a seat in said otheleg receiving said ball bearing.

8. A temperature control device comprising a thermostat bar having oneend tree to move in response to changes in temperature, a spring havingone end bearing on said free end and movable with said bar in its planeof movement so as to cause said bar to move quickly trom one position toanother, a support for the other end of'said spring, a pivoted membercarrying said support for movement in said plane of movement of saidthermostat bar, an adjusting screw having an abutment thereon arrangedto engage said pivoted member to shii't its position in one direction insaid plane oi movement when said screw is turned in one direction. asecond abutment fixed on said screw so as to move with it when saidscrew is adjusted. and a spring between said second abutment and saidmember biasing said member into engagement with said first abutment, thetension in said spring remaining unchanged when said screw is turned toadjust the position oi said member.

WALLACE J. E'I'I'INGER.

NICHOLAS MILLER.

